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Update engine to use new interface

This commit is contained in:
Dylan MacKenzie 2020-09-26 13:12:51 -07:00
parent 4c5f9f742c
commit 43e6ef876f
1 changed files with 63 additions and 73 deletions
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136
compiler/rustc_mir/src/dataflow/framework/direction.rs
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@ -1,10 +1,10 @@
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::{self, BasicBlock, Location};
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::ty::TyCtxt;
use std::ops::RangeInclusive;
use super::visitor::{ResultsVisitable, ResultsVisitor};
use super::{Analysis, Effect, EffectIndex, GenKillAnalysis, GenKillSet};
use super::{Analysis, Effect, EffectIndex, GenKillAnalysis, GenKillSet, SwitchIntTarget};
pub trait Direction {
fn is_forward() -> bool;
@ -425,8 +425,8 @@ impl Direction for Forward {
fn join_state_into_successors_of<A>(
analysis: &A,
tcx: TyCtxt<'tcx>,
body: &mir::Body<'tcx>,
_tcx: TyCtxt<'tcx>,
_body: &mir::Body<'tcx>,
dead_unwinds: Option<&BitSet<BasicBlock>>,
exit_state: &mut A::Domain,
(bb, bb_data): (BasicBlock, &'_ mir::BasicBlockData<'tcx>),
@ -489,50 +489,23 @@ impl Direction for Forward {
}
SwitchInt { ref targets, ref values, ref discr, switch_ty: _ } => {
let enum_ = discr
.place()
.and_then(|discr| switch_on_enum_discriminant(tcx, &body, bb_data, discr));
match enum_ {
// If this is a switch on an enum discriminant, a custom effect may be applied
// along each outgoing edge.
Some((enum_place, enum_def)) => {
// MIR building adds discriminants to the `values` array in the same order as they
// are yielded by `AdtDef::discriminants`. We rely on this to match each
// discriminant in `values` to its corresponding variant in linear time.
let mut tmp = analysis.bottom_value(body);
let mut discriminants = enum_def.discriminants(tcx);
for (value, target) in values.iter().zip(targets.iter().copied()) {
let (variant_idx, _) =
discriminants.find(|&(_, discr)| discr.val == *value).expect(
"Order of `AdtDef::discriminants` differed \
from that of `SwitchInt::values`",
);
let mut applier = SwitchIntEdgeEffectApplier {
exit_state,
targets: targets.as_ref(),
values: values.as_ref(),
propagate,
effects_applied: false,
};
tmp.clone_from(exit_state);
analysis.apply_discriminant_switch_effect(
&mut tmp,
bb,
enum_place,
enum_def,
variant_idx,
);
propagate(target, &tmp);
}
analysis.apply_switch_int_edge_effects(bb, discr, &mut applier);
// Move out of `tmp` so we don't accidentally use it below.
std::mem::drop(tmp);
let SwitchIntEdgeEffectApplier {
exit_state, mut propagate, effects_applied, ..
} = applier;
// Propagate dataflow state along the "otherwise" edge.
let otherwise = targets.last().copied().unwrap();
propagate(otherwise, exit_state)
}
// Otherwise, it's just a normal `SwitchInt`, and every successor sees the same
// exit state.
None => {
for target in targets.iter().copied() {
propagate(target, exit_state);
}
if !effects_applied {
for &target in targets.iter() {
propagate(target, exit_state);
}
}
}
@ -540,37 +513,54 @@ impl Direction for Forward {
}
}
/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is
/// an enum discriminant.
///
/// We expect such blocks to have a call to `discriminant` as their last statement like so:
/// _42 = discriminant(_1)
/// SwitchInt(_42, ..)
///
/// If the basic block matches this pattern, this function returns the place corresponding to the
/// enum (`_1` in the example above) as well as the `AdtDef` of that enum.
fn switch_on_enum_discriminant(
tcx: TyCtxt<'tcx>,
body: &'mir mir::Body<'tcx>,
block: &'mir mir::BasicBlockData<'tcx>,
switch_on: mir::Place<'tcx>,
) -> Option<(mir::Place<'tcx>, &'tcx ty::AdtDef)> {
match block.statements.last().map(|stmt| &stmt.kind) {
Some(mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated))))
if *lhs == switch_on =>
{
match &discriminated.ty(body, tcx).ty.kind() {
ty::Adt(def, _) => Some((*discriminated, def)),
struct SwitchIntEdgeEffectApplier<'a, D, F> {
exit_state: &'a mut D,
values: &'a [u128],
targets: &'a [BasicBlock],
propagate: F,
// `Rvalue::Discriminant` is also used to get the active yield point for a
// generator, but we do not need edge-specific effects in that case. This may
// change in the future.
ty::Generator(..) => None,
effects_applied: bool,
}
t => bug!("`discriminant` called on unexpected type {:?}", t),
}
impl<D, F> super::SwitchIntEdgeEffects<D> for SwitchIntEdgeEffectApplier<'_, D, F>
where
D: Clone,
F: FnMut(BasicBlock, &D),
{
fn apply(&mut self, mut apply_edge_effect: impl FnMut(&mut D, SwitchIntTarget)) {
assert!(!self.effects_applied);
let mut tmp = None;
for (&value, &target) in self.values.iter().zip(self.targets.iter()) {
let tmp = opt_clone_from_or_clone(&mut tmp, self.exit_state);
apply_edge_effect(tmp, SwitchIntTarget { value: Some(value), target });
(self.propagate)(target, tmp);
}
_ => None,
// Once we get to the final, "otherwise" branch, there is no need to preserve `exit_state`,
// so pass it directly to `apply_edge_effect` to save a clone of the dataflow state.
let otherwise = self.targets.last().copied().unwrap();
apply_edge_effect(self.exit_state, SwitchIntTarget { value: None, target: otherwise });
(self.propagate)(otherwise, self.exit_state);
self.effects_applied = true;
}
}
/// An analogue of `Option::get_or_insert_with` that stores a clone of `val` into `opt`, but uses
/// the more efficient `clone_from` if `opt` was `Some`.
///
/// Returns a mutable reference to the new clone that resides in `opt`.
//
// FIXME: Figure out how to express this using `Option::clone_from`, or maybe lift it into the
// standard library?
fn opt_clone_from_or_clone<T: Clone>(opt: &'a mut Option<T>, val: &T) -> &'a mut T {
if opt.is_some() {
let ret = opt.as_mut().unwrap();
ret.clone_from(val);
ret
} else {
*opt = Some(val.clone());
opt.as_mut().unwrap()
}
}